1. Field of the Invention
The present invention relates to a clutch mechanism for a lock. In particular, the present invention relates to a clutch mechanism for a lock that allows the outer handle to rotate freely when the lock is in a locked state so that the internal parts of the lock will not be damaged.
2. Description of the Related Art
A conventional door lock generally includes an outer handle and an inner handle respectively attached to the outside and the inside of a door so that the latch bolt can be retracted by turning either one of the outer handle and the inner handle. When in a locked state, the outer handle could not be turned for retracting the latch bolt. It is, however, not uncommon that the user still applies force to the outer handle to an extent that is normally sufficiently large enough for retracting the latch bolt if the user is not aware of the locked state of the lock. Thus, the inner parts of the lock connected to the handle could be damaged by a torque resulting from the force applied to the outer handle. The situation worsens for a lock with lever type handles.
U.S. Pat. No. 6,041,630 discloses a lock having a clutch mechanism to solve this problem. The lock includes an inner handle having a locking bar received therein and an outer handle connected to a spindle with a retaining base received therein which has two first grooves defined therein. A cam is connected to the retaining base and has two second grooves which communicate with the first grooves so that a locking piece is movably received between the retaining base and the cam with a spring biased between the locking piece and the retaining base. The locking piece has two flanges movably received in the first grooves and the second grooves. A slide is movably received in the cam and contact the locking piece at one end thereof and the locking bar at the other end thereof so that the two flanges of the locking piece are disengaged from the second grooves when the locking bar is pushed. Therefore, the outer handle can be freely rotated. Nevertheless, there are too many elements for the clutch mechanism. The assembly procedure is too complicated and the overall cost is increased.
An object of the present invention is to provide a clutch mechanism for a lock that allows easy assembly and that is easy to manufacture while allowing the outer handle to rotate freely when the lock is in a locked state so that the internal parts of the lock will not be damaged.
A lock mechanism in accordance with the present invention comprises:
a latch;
a retractor for retracting the latch;
an inside handle;
an inside spindle having a first end fixed to the inside handle to turn therewith and a second end, the inside spindle being operably connected to the retractor such that rotation of the inside spindle causes retraction of the latch;
a locking bar extending through the inside spindle and having a first end and a second end;
an inside hub for rotatably receiving the second end of the inside spindle;
an outside handle;
an outside spindle having a first end and a second end fixed to the outside handle to turn therewith, the first end of the outside spindle including a slot extending along a longitudinal direction of the outside spindle;
an outside hub for rotatably receiving the first end of the outside spindle;
a cam received in the first end of the outside spindle, the cam being movable relative to the outside spindle along a longitudinal direction of the outside spindle, the cam having an engaging notch, the cam further having an ear projecting outward therefrom, the ear of the cam being releasably engaged with the retractor such that rotation of the cam causes retraction of the latch;
a sleeve received in the cam and having a first end and a second end;
a lug having an arm and a ring formed on an end of the arm, the ring being so mounted to the first end of the sleeve that the sleeve is not turned when the arm is turned and that the arm and the sleeve are jointly movable along the longitudinal direction of the outside spindle, the arm extending through the engaging notch of the cam and the slot of the outside spindle, the cam and the outside spindle being turned jointly when the outside handle is turned; and
an elastic element mounted between the outside handle and the cam for biasing the ear of the cam to engage with the retractor;
wherein when the locking bar is moved to a locking position, the lug and the sleeve are moved away from the retractor, the cam is also moved away from the retractor such that the ear of the cam is disengaged from the retractor, allowing free rotation of the outside handle without causing retraction of the latch.